The disclosure relates to membrane roofing systems and more particularly to a tool for marking locations on a roof membrane corresponding to bonding plates concealed below the roof membrane.
A bonding plate is a metal plate, typically made of steel, partially coated with adhesive and used to secure a roof membrane to a roof structure. The bonding plate is held in place by fasteners that extend through the bonding plate and a rigid insulation layer (if present) to engage a roof deck. The adhesive is heat activated (hot melt) and located on a raised, annular platform of the bonding plate which surrounds a recess for the fastener. The plates are heated using an induction heating apparatus that generates a high frequency oscillating magnetic field. The magnetic field penetrates the roof membrane and induces heating of the bonding plate. The heat activates the adhesive such that it affixes the bonding plate to the underside of the roof membrane. After heating, as the roof membrane and bonding plate cool, a powerful magnet is typically placed atop the roof membrane at the location of the bonding plate to assist in adhesion between the roof membrane and the bonding plate. The heating apparatus is then be moved to another bonding plate while previously heated bonding plates are allowed to cool with pressure applied to the roof membrane and the bonding plate.
Roof membranes are produced in varying thicknesses, ranging from 30 to 80 mils and are manufactured from different materials including TPO, EPDM and PVC. Some roof membranes may be layered in construction, having specific materials at different depths to attain a desired membrane property.
Clearly identifying the location of each bonding plate beneath the roof membrane is critical to ensuring that each plate is heated and pressed while cooling to establish a high-integrity bond between the roof membrane and the bonding plate. However, once the roof membrane is laid down atop the bonding plates, the bonding plates are effectively concealed and can be difficult to locate. The thickness, composition, material and ambient temperature all impact the flexibility of the roof membrane and the visibility of the bonding plate. When temperatures are warm and the roof membrane is thin, the roof membrane is pliable and drapes over the slightly raised bonding plates in a manner that may allow the contours of the bonding plates to be visible by eye through the roof membrane. When temperatures are cooler and the roof membrane is thicker, the membrane can be stiff, making bonding plates nearly impossible to visually detect. Under these circumstances, workers may use their shoes to scuff the surface of the roof membrane to determine the location of the bonding plates. Methods such as this can damage the roof membrane and can be extremely inefficient.
Therefore, there is a need for an apparatus that can assist workers in detecting and marking locations on a roof membrane corresponding to the location of bonding plates positioned beneath the roof membrane.